This is really well produced, and lets viewers see history in a new perspective. It separates military and civilian deaths by country, by year and by events. The video also compares conflicts before and after WW2, both in total deaths and proportion of world population lost.
There were more devastating conflicts than WW2 in the past, and nothing comes close to the scale of WW2 since, not even when you combine them all.
China suffered huge military and civilian losses, but in return inflicted very little Japanese military casualties. The intentional breach of yellow river dam at Huayuankou by the KMT killed more people than the 2004 Indian Ocean Tsunami.